The present invention relates to a stirring apparatus suitable for mixing and stirring liquid continuously. More particularly, the present invention relates to improvements in a stirring apparatus, the processing speed of which is increased and the processing quality of which is enhanced when mixing and stirring are sufficiently conducted so as to obtain fine particles of uniform particle size.
FIG. 4 is a sectional view showing a conventional example of an apparatus for continuous operation capable of mixing and stirring liquid continuously while liquid is being supplied, which was available through Sinmaru Enterprises Co., and was produced by Willy A. Bachstex Co.
In FIG. 4, the apparatus comprises a substantially cylindrical vessel 2 and a plurality of stirring impellers 3 rotated in the vessel 2.
The vessel 2 is a substantially closed container, at one end of which a liquid supply port 4, into which liquid to be stirred is made to flow, is provided, and at the other end of which a liquid discharge port 5, from which stirred liquid is discharged, is provided.
There are provided a plurality of stirring impellers 3, which are fixed onto a sleeve 7 engaged with a rotational shaft 6 penetrating through the other end wall of the vessel 2. The plurality of stirring impellers 3 are rotated integrally with the rotational shaft 6 via the sleeve 7, so that liquid can be stirred in the vessel 2. The rotational shaft 6 is driven and rotated by a motor not illustrated in the drawing.
According to the above arrangement, liquid is supplied from the supplied liquid supply port 4 into the vessel 2. Then the liquid is stirred when the stirring impellers 3 are rotated, and then discharged from the liquid discharge port 5. Therefore, it is possible to conduct stirring continuously. This apparatus is disclosed in U.S. Pat. No. 2,581,414.
However, according to the above arrangement of the conventional apparatus, the following problems may be encountered. Since all stirring impellers 3 are rotated in the same direction, liquid in the stirring tank tends to flow in a steady state. Accordingly, when the rotational shaft 6 is rotated at higher speed so as to increase the processing speed of the stirrer, cavities are generated around the sleeve 7 which is located at the center of the vessel 2. Due to the foregoing, there is a remarkable tendency that the liquid to be mixed and stirred is pushed against the inner circumferential surface of the vessel 2. As a result, the liquid flows along the inner circumferential surface of the vessel 2 without being sufficiently stirred. Accordingly, quality of the processed liquid is deteriorated. For the above reasons, it is difficult to increase the processing speed.
In a portion on the end wall of the vessel 2 where the rotational shaft 6 penetrates, that is, in a shaft penetrating portion, it is necessary to provide a sealing property for preventing liquid from leaking outside the vessel, and also it is necessary to provide a lubricating property required when the rotational shaft 6 is rotated at high speed. In order to satisfy both the necessary properties, liquid seal is usually adopted for the sealing means. However, it is very difficult to maintain the liquid seal in an ideal condition. In some cases, lubricant (sealing liquid) used as a liquid seal is mixed into the vessel 2 as impurities, which deteriorates the quality of the processed liquid.
In the case where the liquid to be stirred is used as a lubricant, it is necessary to clean the lubricant, which is very difficult.